Choose the answers that best represent appropriate sign and magnitude conventions for finding the torque about a pivot. Select all that you consider to be true.

Question

BlackTom AI · Accepted Answer

Let’s break down each statement in light of torque concepts and a standard sign convention where positive torque is counterclockwise and negative torque is clockwise.
Option 1: 'Counter-Clockwise torques are negative' — Under the common convention stated above, counterclockwise torques are positive, not negative. This makes the claim incorrect because it swaps the sign assignment for CCW torques.
Option 2: 'Forces acting through the pivot point produce zero torque' — If a force acts exactly at the pivot, the lever arm is zero, so the torque r × F has magnitude zero regardless of the force, meaning no rotational effect about that pivot. This statement is correct.
Option 3: 'Forces acting a distance (moment arm) away from the pivot point produce no torque' — This is false in general. A force applied at a distance from the pivot typically produces torque proportional to the lever arm length and the sine of the angle between r and F. Only in special cases where the force is directed radially toward or away from the pivot (or along the line through the pivot) would the torque be zero. In general, a nonzero moment arm yields a nonzero torque.
Option 4: 'Clockwise torques are negative' — With the standard convention where clockwise tends to rotate in the negative (opposite to CCW positive) direction, this statement is correct. Clockwise torques carry negative sign under that convention.
In summary, evaluating each option against the conventional definitions shows that the true statements are those about forces through the pivot producing zero torque and clockwise torques being negative, while the CCW negative claim and the general no-torque-with-distance claim do not hold under the typical torque-sign convention.

PS 113L TASK: Pre-Lab Quiz: Torque

Choose the answers that best represent appropriate sign and magnitude conventions for finding the torque about a pivot. Select all that you consider to be true.

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